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Register a new userMeasurement of CP asymmetry in $B^0_s rightarrow D^{mp}_s K^{pm}$ decays
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We report on measurements of the time-dependent CP violating observables in $B^0_srightarrow D^{mp}_s K^{pm}$ decays using a dataset corresponding to 1.0 fb$^{-1}$ of pp collisions recorded with the LHCb detector. We find the CP violating observables $C_f=0.53pm0.25pm0.04$, $A^{DeltaGamma}_f=0.37pm0.42pm0.20$, $A^{DeltaGamma}_{bar{f}}=0.20pm0.41pm0.20$, $S_f=-1.09pm0.33pm0.08$, $S_{bar{f}}=-0.36pm0.34pm0.08$, where the uncertainties are statistical and systematic, respectively. Using these observables together with a recent measurement of the $B^0_s$ mixing phase $-2beta_s$ leads to the first extraction of the CKM angle $gamma$ from $B^0_s rightarrow D^{mp}_s K^{pm}$ decays, finding $gamma$ = (115$_{-43}^{+28}$)$^circ$ modulo 180$^circ$ at 68% CL, where the error contains both statistical and systematic uncertainties.
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A measurement of the $CP$ asymmetries $S_{f}$ and $S_{bar{f}}$ in $B^0to D^{mp}pi^{pm}$ decays is reported. The decays are reconstructed in a dataset collected with the LHCb experiment in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV and corresponding to an integrated luminosity of $3.0 rm{ fb}^{-1}$. The $CP$ asymmetries are measured to be $S_{f} = 0.058 pm 0.020 (rm{stat}) pm 0.011(rm{syst})$ and $S_{bar{f}} = 0.038pm 0.020 (text{stat})pm 0.007 (text{syst})$. These results are in agreement with, and more precise than, previous determinations. They are used to constrain $|sinleft(2beta+gammaright)|$ and $gamma$ to intervals that are consistent with the current world-average values.
A measurement of the time-integrated $CP$ asymmetry in $D^0rightarrow K^0_S K^0_S$ decays is reported. The data correspond to an integrated luminosity of about $2$ fb$^{-1}$ collected in 2015-2016 by the LHCb collaboration in $pp$ collisions at a centre-of-mass energy of $13$ TeV. The $D^0$ candidate is required to originate from a $D^{ast +} rightarrow D^0 pi^+$ decay, allowing the determination of the flavour of the $D^0$ meson using the pion charge. The $D^0 rightarrow K^{+}K^{-}$ decay, which has a well measured $CP$ asymmetry, is used as a calibration channel. The $CP$ asymmetry for $D^0rightarrow K^0_S K^0_S$ is measured to be begin{equation*} mathcal{A}^{CP}(D^0rightarrow K^0_S K^0_S) = (4.3pm 3.4pm 1.0)%, end{equation*} where the first uncertainty is statistical and the second is systematic. This result is combined with the previous LHCb measurement at lower centre-of-mass energies to obtain begin{equation*} mathcal{A}^{CP}(D^0rightarrow K^0_S K^0_S) = (2.3pm 2.8pm 0.9)%. end{equation*}
The decay-time-dependent $CP$ asymmetry in $B^0 to D^{*pm}D^{mp}$ decays is measured using a data set corresponding to an integrated luminosity of $9$fb$^{-1}$ recorded by the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV. The $CP$ parameters are measured as $ S_{D^*D} = -0.861 pm 0.077,text{(stat)} pm 0.019 ,text{(syst)},, $ $ Delta S_{D^*D} = 0.019 pm 0.075 ,text{(stat)} pm 0.012 ,text{(syst)} ,, $ $ C_{D^*D} = -0.059 pm 0.092 ,text{(stat)} pm 0.020 ,text{(syst)} ,, $ $ Delta C_{D^*D} = -0.031 pm 0.092 ,text{(stat)} pm 0.016 ,text{(syst)} ,, $ $ {cal A}_{D^*D} = 0.008 pm 0.014 ,text{(stat)} pm 0.006 ,text{(syst)},. $ The analysis provides the most precise single measurement of $CP$ violation in this decay channel to date. All parameters are consistent with their current world average values.
The CKM angle $gamma$ is measured for the first time from mixing-induced $CP$ violation between $B^0_s rightarrow D_s^mp K^pm pi^pm pi^mp$ and $bar{B}^0_s rightarrow D_s^pm K^mp pi^mp pi^pm$ decays reconstructed in proton-proton collision data corresponding to an integrated luminosity of 9 ${rm fb}^{-1}$ recorded with the LHCb detector. A time-dependent amplitude analysis is performed to extract the $CP$-violating weak phase $gamma-2beta_s$ and, subsequently, $gamma$ by taking the $B^0_s$-$bar{B}^0_s$ mixing phase $beta_{s}$ as an external input. The measurement yields $gamma = (44 pm 12)^circ$ modulo $180^circ$, where statistical and systematic uncertainties are combined. An alternative model-independent measurement, integrating over the five-dimensional phase space of the decay, yields $gamma = (44^{,+,20}_{,-,13})^circ$ modulo $180^circ$. Moreover, the $B^0_s$-$bar{B}^0_s$ oscillation frequency is measured from the flavour-specific control channel $B^0_s rightarrow D_s^- pi^+ pi^+ pi^-$ to be $Delta m_s = (17.757 pm 0.007 ,({rm stat.}) pm 0.008 ,({rm syst.})) text{ps}^{-1}$, consistent with and more precise than the current world-average value.
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